Urfa Cheese Research Articles

SCREENING OF ANTIBIOTIC RESISTANCE AND VIRULENCE GENES OF ENTEROCOCCUS SPP. STRAINS ISOLATED FROM URFA CHEESE

Enterococcus faecium, E. durans and E. faecalis species were isolated and identified from traditional Urfa cheese samples which were produced from unpasteurized raw milk. The enterococcal load of the cheese samples was between 4.4-5.6 log cfu g−1. High-level tetracycline, streptomycin, erythromycin, gentamycin, and penicillin resistance was determined in the enterococcal isolates. Multiple antibiotic resistance was also determined in E. faecalis (20.4%) and E. faecium (16.3%) strains. 36.7% of the enterococcal isolates were greater than 0.2 MAR index ratio in this study. The gelE and agg2 genes were found in 40 (81.63%) of the enterococcal isolates, whereas the vanB gene was found in 3 (6.12%) of the enterococcal isolates. The results indicate that the consumption of Urfa cheese, which is produced using raw milk, may have public health risk because of its antibiotic resistance characteristics and virulence genes of enterococcal biota.

Effects of Scalding Temperature, Scalding Time and Ripening Time on the Chemical, Textural and Microstructural Properties of Ovine Milk Urfa Cheese

The objectives of this study were to determine the effect of cheese scalding temperature, scalding time, and ripening time on the chemical, textural and microstructural properties of ovine milk Urfa cheese. Dry salted fresh cheeses were scalded in whey at 70 °C, 80 °C, and 90 °C for 5 and 10 minutes and ripened for 90 days, respectively. Scalding temperature significantly affected fat in dry matter and salt in dry matter (P<0.05), total solids and nitrogen, hardness, cohesiveness, gumminess, and chewiness (P<0.001). Scalding time significantly affected total nitrogen and gumminess (P<0.05), total solids, and hardness (P<0.001). Ripening time significantly affected chemical, textural and color properties of ovine milk Urfa cheese (P<0.001), except fat in dry matter (P<0.05). The color properties of Urfa cheese were not significantly affected by the scalding temperature and time (P>0.05). Besides, scalding treatments have improved the microstructure of ovine milk Urfa cheeses. Urfa cheese exhibited a more compact, coarser, and uniform structure with increasing scalding temperature and time. As a result, scalding treatments and ripening on the chemical, textural and microstructural characteristics of Urfa cheeses were substantially effective.

Determination of some minerals and heavy metal levels in Urfa cheese and cow's milk

This research was carried out to determine the levels of some minerals and heavy metals in Urfa cheeses and cow's milk offered for sale in Şanlıurfa. Mineral and heavy metal levels were determined by analysing 18 Urfa cheese and 21 cow milk samples collected from retail outlets with ICP-MS. Mean mineral and heavy metal contents in Urfa cheese samples were; magnesium (Mg) 129.8 ±31.14 mg/kg, calcium (Ca) 2712.66 ±1002.4 mg/kg, potassium (K) 272.06 ±127.21 mg/kg, titanium (Ti) 7.48 ±2.63 mg/kg, zinc (Zn) 40.4 ±16.33 mg/kg, selenium (Se) 10.6 ±3.51 mg/kg. In cow milk samples, average selenium (Se) 0.22 ±0.04 mg/kg, titanium (Ti) 0.07 ±0.009, mg/kg, copper (Cu) 0.0068 ±0.01 mg/kg and chromium (Cr) was detected at the level of 0.019 ±0.001 mg/kg. Arsenic (As), cadmium (Cd), lead (Pb) and thallium (Tl) levels were below the detectable levels in Urfa cheese and cow's milk samples. As a result, it was concluded that the samples do not pose a significant danger to public health in terms of heavy metal pollution and can contribute significantly to nutrition with the mineral substances it contains.

Effects of partial substitution of goat's milk for sheep's milk, cured scalding and dry salting on proteolysis in Urfa cheese

The effects of partial substitution of goat's milk for sheep's milk, scalding and dry salting on the proteolysis of Urfa cheese were monitored for 240 days. For this reason, the contents of total nitrogen, water-soluble nitrogen (WSN), and trichloroacetic acid-soluble nitrogen (TCA-SN) were explored as well as the chemical compositions of samples during ripening. Also, RP-HPLC of pH 4.6-soluble, 70% ethanol-insoluble (EtOH-i), and urea-PAGE of pH 4.6-insoluble nitrogen fractions of samples was determined. The results showed that the effects of partial substitution of goat's milk for sheep's milk on WSN and TCA-SN were significant from sixth to eighth month of the ripening, respectively. Even though the effects of the milk type, dry salting, and scalding on the peptide profile were significant at the beginning of maturation, the peptide profile of cheeses was almost similar at the end of the storage. Furthermore, the proteolysis of Urfa cheese was limited due to dry salting during the ripening. Practical applications The maturation of cheese is a complex biochemical process involving the hydrolysis of fat, breakdown of protein, and metabolism of lactose. Though the biochemical reactions during cheese ripening are not precisely understood, proteolysis is one of the most significant biochemical processes during maturation. It is known that the amino acids resulting from proteolysis are the precursors of flavor components in cheese. Milk itself is a significant source of proteolytic enzymes. And also, the curd scalding temperature and salt content of cheese affect the proteolytic activity during cheese ripening. However, limited proteolysis may be occurred during the cheese maturation due to dry salting and scalding process. Therefore, studies should focus on overcoming this problem. This study can help to overcome the limited proteolysis in the production of cheese. Also, results from the study may contribute to the industrial production of Urfa cheese.

Effect of Wild Strains Used as Starter Cultures on Free Fatty Acid Profile of Urfa Cheese

Effect of Wild Strains Used as Starter Cultures on Free Fatty Acid Profile of Urfa Cheese

Identification and characterisation of lactic acid bacteria isolated from traditional Urfa cheese

In this study, characterisation of dominant strains of lactic flora in traditional Urfa cheese made from sheep's milk was performed using biochemical, phenotypic and genotypic methods. According to the results obtained, the percentage distributions of the lactic acid bacteria isolated were as follows: 48.95% Enterococcus spp., 40.55% Lactococcus spp., 9.10% Lactobacillus spp., 0.69% Streptococcus spp. and 0.69% Leuconostoc spp. The majority of lactococcal isolates showed an atypical phenotype of growing in the presence of 6.5% NaCl. Acidification and bacteriocin production were also determined for each isolate. Four strains showed bacteriocin activity.

Effects of Wild-Type Starter Culture (Artisanal Strains) on Volatile Profile of Urfa Cheese Made from Ewe Milk

In the present study, the development of volatile flavor compounds in sheep’s milk Urfa cheese made by using three different combinations of wild-type strains including Lactococcus lactis subsp. lactis 1B4, Lactococcus garvieae IMAU 50157, Enterococcus faecium ATCC 19434, Enterococcus durans IMAU 60200, and Enterococcus faecalis KLDSO.034 was investigated over 180 days. Three batches of cheese were made using above strains as follows: Cheese A (strains ATCC 19434+1B4+IMAU 50157); Cheese B (strains IMAU 60200+ATCC 19434+1B4); Cheese C (strains KLDSO.034+ IMAU 60200+ ATCC 19434+1B4+ IMAU 50157). The fourth batch was produced from raw sheep’s milk as control (Cheese D). The volatile compounds were identified using a gas chromatography/mass spectrometry system combined with solid-phase microextraction. In total, 70 volatile compounds were recovered from the cheeses including 10 alcohols (mainly ethanol, 2-methyl-1-propanol, 3-methyl-1-propanol), 20 aldehydes and ketones (mainly 2-pentanone, 2-heptanone), 11 esters (mainly ethyl acetate), 10 acids (mainly acetic acid, 2-hydroxy-4-methyl pentanoic acid), 6 terpenes (mainly α-pinene), and 13 miscellaneous compounds (mainly 3,7-dimethyl-1,6-octadiene). While total aldehydes concentration in the control cheese was higher than those made from combinations of wild-type strains (Cheeses A to C), the concentration of alcohols was lower in the former sample. Regarding other volatile compounds there was no clear differences between the cheeses. Results showed that strain combination A or C (Cheese A or C, respectively) could be employed in the manufacture of Urfa cheese made from pasteurized sheep’s milk. However, to reach a fair judgement on the proper strain combination for Urfa cheese, aroma profile (i.e., active compounds) released by the strains should be laid open in detail.

Evolution of proteolysis in Urfa cheese made from ewe's milk by wild type starter culture systems

The evolution of proteolysis in Urfa cheese made from ewe's milk by using various combinations of wild-type strains of Lactococcus lactis (strain 1B4), Lactococcus garvieae (strain IMAU 50157), Enterococcus faecalis (strain KLDSO.0341), Enterococcus faecium (strain ATCC 19434) and Enterococcus durans (strain IMAU 60200) was monitored for 180 days. The strains used in the study were isolated from traditional raw ewe's milk Urfa cheese and characterized by phenotypic and genotypic studies previously. Three different combinations of the strains were employed in the manufacture of cheeses from pasteurized milk. These are: cheese A (strains 1B4+ATCC 19434+IMAU 50157), cheese B (strains 1B4+IMAU 60200+ATCC 1934) and cheese C (strains ATCC 19434+1B4+IMAU 50157+IMAU 60200+KLDSO.0341). The control cheese (cheese D) was produced from raw ewe's milk without starter culture. Proteolysis in the cheeses was evaluated using urea-PAGE of pH 4.6-insoluble and RP-HPLC of both 70% ethanol-insoluble (EtOH-i) and ethanol-soluble (EtOH-s) nitrogen fractions. The variations in water soluble nitrogen (WSN) and trichloroacetic acid-soluble nitrogen (TCA-SN) were also monitored during ripening as well as gross compositions of the cheeses. Results indicated that the degradation of casein fractions were faster in the cheeses A, B and C than the control. The peptide profiles of 70% EtOH-i and EtOH-s nitrogen of the cheeses A, B and C were close to each other but far more extensive than the control cheese. The proteolytic capacities of the strains employed in the cheeses A, B and C were superior to that of raw milk flora. To conclude, any of the combinations of the wild-type strains could be used in the production of Urfa cheese from pasteurized ewe's milk, as long as the safe use of enterococcal strains is assured.

Effects of partial substitution of caprine for ovine milk on the volatile compounds of fresh and mature Urfa cheeses

Fresh Urfa cheeses were produced from ovine and caprine milk mixed in ratios of 100:0; 90:10; 80:20; 70:30 (ovine:caprine). They were preserved by two methods: (1) dry salted for 12h, and (2) scalded in boiling whey for 5min and ripened for 240 days. The basic composition of ovine cheese did not significantly differ from cheese, in which part of the sheep milk was replaced by goat's milk. The composition of dry salted cheese was in general similar with scalded cheese for chemical compositions and volatile compounds. Alcohols were quantitatively the most abundant chemical family found in the Urfa cheese, and their concentration were 37.91–53.48μg100g−1 fresh cheese, especially more marked in the mature cheeses (56.21–121.54μg100g−1 cheese). After 3 months, the concentration of volatile compounds and their contents of Urfa cheese generally decreased. Thus, Urfa cheese could be matured until 90 days in brine without affecting the concentration of volatile compounds. The partial substitution of ovine milk with caprine milk by up to 10 and 20% did not generally change volatile characteristics of the cheese. However, 30% substitution of ovine milk with caprine milk increased hexanoic, octanoic, decanoic acids, 2-methyl-pentanal, 2-butanone, 2-heptanone, 2-nonanone, methyl butanoate, and decreased acetic acid, 3-methyl-butanal, heptanal, 3-hydroxy-2 butanone, and methyl-2-methyl-butanoate.

Characterization of Staphylococcus aureus isolates from white-brined Urfa cheese.

The aim of this study was to investigate the presence of Staphylococcus aureus and staphylococcal enterotoxin (SE) genes in Urfa cheese samples and to characterize the enterotoxigenic potential of these isolates. From a total of 127 Urfa cheese samples, 53 isolates (from 41.7% of the samples) were identified by a species-specific PCR assay as S. aureus. Of these isolates, 40 (75.5%) gave positive PCR results for the 3' end of the coa gene. The coa-positive S. aureus strains were characterized for their population levels and enterotoxigenic properties, including slime factor, β-lactamase, antibiotic susceptibilities, production of the classical SEs (SEA through SEE), in both cheese and liquid cultures by enzyme-linked immunosorbent assay (ELISA) and for the presence of specific genes, including classical SE genes (sea through see), mecA, femA, and spa, by PCR. The genetic relatedness among the coa-positive S. aureus isolates was investigated by PCR-based restriction fragment length polymorphism (RFLP) analysis and the 23S rRNA gene spacer. The 23S rRNA gene spacer and coa RFLP analysis using AluI and Hin6I revealed 14 different patterns. SEB, SEC, and SEA and SEE were detected by ELISA in three cheese samples. Fourteen S. aureus strains harbored enterotoxin genes sea through see, and three strains carried multiple toxin genes. The most commonly detected toxin gene was sec (25% of tested strains). Of the 40 analyzed S. aureus strains, 3 (7.5%) were mecA positive. Based on tandem repeats, four coa and spa types were identified. The results of this study indicate that S. aureus and SEs are present at significant levels in Urfa cheese. These toxins can cause staphylococcal food poisoning, creating a serious hazard for public health.

Detection of aflatoxin M1 levels by ELISA in white-brined Urfa cheese consumed in Turkey

Aflatoxin M1 (AFM1) is the hydroxylated metabolite of aflatoxin B1 found in a variety of foods. In this study, 127 samples of white-brined Urfa cheese produced mainly in the southeast of Turkey from raw ovine and bovine milks were surveyed for the presence of AFM1 using a competitive Enzyme Linked Immunosorbent Assay (ELISA) technique. The results showed that at detectable levels (≥50 ng/kg), 36 cheese samples (28.3%) were contaminated with AFM1 ranging from 70.61 to 770.97 ng/kg. Of the 36 cheese samples, 13 (10.2%) were found to have levels that exceeded the legal limits of 250 ng/kg established by the Turkish Food Codex. Consequently, the AFM1 contamination levels determined in this study in white-brined Urfa Cheese, which is commonly consumed in the southeast part of Turkey, were not considered to be a serious public health hazard. It was considered to be a potential risk for customers, particularly for infant health.

Lipolysis in Urfa cheese produced from raw and pasteurized goats’ and cows’ milk with mesophilic or thermophilic cultures during ripening

Lipolysis was evaluated in Urfa cheese made from raw and pasteurized goats’ and cows’ milk with mesophilic or thermophilic cultures. The acid degree values (ADVs) of the cows’ milk cheeses were significantly ( P < 0.05) higher until 60 d of storage than that of cheese made from goats’ milk. Total free fatty acid (FFA) contents of goats’ milk cheese were significantly ( P < 0.001) lower than that of cows’ milk cheese throughout ripening, whereas goats’ milk cheese flavour was higher ( P < 0.05) than cows’ milk cheese. Pasteurization of milk prior to cheese-making has a negative influence, not only on the level of lipolysis throughout ripening, but also on the relative amounts of short chain FFAs and sensory properties of the cheeses ( P < 0.001). Cheese produced without starter bacteria underwent significantly ( P < 0.05) higher lipolysis than cheeses produced with mesophilic or thermophilic starter bacteria, while cheese made with thermophilic starter culture had similar flavour to cheese made without starter culture.

Microflora and Pathogen Bacteria (Salmonella, Klebsiella, Yersinia, Pseudomonas, Aeromonas, Escherichia coli, Staphylococcus aureus) In Urfa Cheese (A Traditional White-Brined Turkish Cheese)

2 Abstract: Urfa cheese is normally produced from ovine or bovine milk or appropriate mixture of these two especially in Urfa. Urfa cheeses are being manufactured, as regional, by the use of raw milk or scalded milk that has been heated up to 30-35 C. This cheese use to be consumed in the region, without waiting the o completion of its maturation period. Gastroenteritis case number in Urfa is considerably high as compared to the other regions. For these reasons 11 different Urfa regional cheeses have been purchased within their brine concentration. They were studied during 0-7th, 30th and 60th day as regard to micro flora and pathogen microorganisms. At the end of micro flora research of Urfa cheeses, Escherichia, Salmonella, Enterobacter, Klebsiella, Pseudomonas, Yersinia, Aeromonas, Hafnia, Serratia, Morgenella and also Cedecea, Citrobacter, Hafnia have been detected. Besides, Staphylococcus (S. aureus) has been determined therein. Steptococcus, Lactococcus, Lactobacillus, Pediococcus, Leuconostoc were identified as well. In our research we have detected that the variety of micro organism are quite a lot in Urfa cheeses. We identified various pathogen bacteria also. It has recommended that the region's people not consume fresh Urfa cheese.

Effects of heat treatment and starter culture on the properties of traditional Urfa cheeses (a white-brined Turkish cheese) produced from bovine milk

The objective of the present research was to determine the effects of heat treatment and starter culture on some properties of Urfa cheese produced from bovine milk. Proteolysis developed more rapidly in the cheese made with mesophilic starter culture. Whereas the cheese inoculated with thermophilic starter culture received higher sensory scores. High heat treatment (at 72 °C for 5 min) affected the sensory and chemical properties of Urfa cheese adversely. Therefore, incorporation of low heat treatment (at 65 °C for 20 min) is recommended for the production of Urfa cheese, with addition of a culture of Lactococcus lactis subsp. lactis + Lactococcus lactis subsp. cremoris.

Identification of enterobacteriaceae in Urfa cheese

The purpose of this study was to determine the Enterobacteriaceae counts and to identify the species isolated in Urfa cheese traditionally manufactured from raw milk in Sanliurfa. In the research, 75 samples obtained from retail markets were examined. Enterobacteriaceae was detected in 45.33% of the samples and counts varied between 10 2 –10 8 CFU g −1 . A total of 8 different species were identified, the most common of those was Klebsiella pneumonia (30% of the isolated strains), followed by Escherichia coli (25.29%), Enterobacter cloacea (16.47%) and Enterobacter aerogenes (11.76%). Klebsiella oxytoca , Citrobacter freundii, Yersinia enterocolitica and Serratia marcescens were present in small quantities (7.06, 5.88, 2.45 and 1.18% of the isolates, respectively). The results obtained from this study clearly indicate that measures should be taken to control and reduce the contamination and multiplication of pathogens such as E. coli , Y. enterocolitica and other Enterobacteriaceae spp. in Urfa cheese.

The effects of brine concentration and scalding on survival of some pathogens in urfa cheese: a traditional white‐brined turkish cheese

SummaryThe survival of Staphylococcus aureus (St. aureus), Bacillus cereus, Yersinia enterocolitica, Eschericia coli O157:H7, Shigella flexneri (Sh. flexneri) and Salmonella enteritidis (Sa. enteritidis) in urfa cheese (a traditional white‐brined Turkish cheese) which was stored in brine concentrations varying from 12.5 to 17.5% (wt/v) was tested. Two sets of cheeses were made, namely scalded and unscalded cheeses (scalding was done by heating at 95 °C for 3 min). The variations in the counts of pathogenic colonies were monitored throughout a 90‐day storage period at &lt;10 °C. Results indicated that scalding caused statistically significant reductions in the colony counts of Y. enterocolitica, E. coli O157:H7, Sh. flexneri and Sa. enteritidis during the early periods of storage. In contrast, St. aureus and B. cereus were not generally affected by scalding and brine concentrations, although B. cereus in 17.5% (wt/v) brine was affected. In the unscalded cheeses, 12.5 and 15.0% (wt/v) brine concentrations seemed to be insufficient to eradicate the pathogenic organisms examined.

Textural and microstructural properties of urfa cheese (a white‐brined Turkish cheese)

The texture and microstructure of white‐brined cheeses similar to urfa (a traditional Turkish cheese) were studied. One batch of cheeses was made in the traditional manner and one batch was made from ultrafiltered (UF) milk. Samples from each batch were either ripened in brine after production or scalded in whey for 3 min at 90°C prior to ripening. The results showed only marginal differences in the ripening profiles of both batches of unscalded cheeses, but scalding slowed down the extent of proteolysis in both batches. The scalded cheeses had a firmer texture than the unscalded ones, and the unscalded UF cheese had a more ‘springy’ body than the unscalded traditional cheese. Overall, scalding resulted in a more homogeneous structure, but the unscalded UF cheese had a close texture that resembled the scalded samples. It was concluded that, with respect to texture and structure, cheeses made with UF milk do not need to be scalded after production.

BIOGENIC AMINE CONTENT OF SOME TURKISH CHEESES

Biogenic amines in ten samples of Kaşar (aged), five samples of Kaşar (fresh), four samples of Mihaliç, nine samples of Van Otlu (herbed), nine samples of Örgü, nine samples of Urfa and six samples of Civil cheeses were obtained from local supermarkets of Ankara. Tryptamine (TRY), phenylethylamine (PHA), putrescine (PUT), cadaverine (CAD), histamine (HIT), tyramine (TYA), spermine (SPM) and spermidine (SPD) contents of Turkish cheese samples were screened by high performance liquid chromatography (HPLC). PUT, CAD, HIT, TYA and SPD were the predominant biogenic amines in maturated Kaşar (aged), vacuum-packed Kaşar (fresh), Mihaliç, Otlu (herbed) and Örgü cheeses. PHA, CAD, TYA and SPD were the predominant biogenic amines in Urfa cheese samples. Civil cheeses were found to contain the highest HIT and TYA content with an average of 94.76 mg/100 g and 138.16 mg/100 g, respectively, much higher than the toxic dose. HIT level of Mihaliç cheeses were also higher than the accepted limit. The concentration of amines in all other cheeses was much lower than the toxic dose limits.

Some properties of urfa cheese (a traditional white‐brined Turkish cheese) produced from bovine and ovine milks

In this study, the basic composition and ripening profile of traditional urfa cheese made from ovine and bovine milks were investigated. While cheese made from ovine milk had higher total solids, fat‐in‐dry matter and total nitrogen, the titratable acidity, salt‐in‐dry matter, pH, total mesophilic colony count and total yeasts and moulds counts were found to be close to each other. During storage, whilst the total solids content of cheese produced from ovine milk gradually decreased, the variation in the total solids content of cheese made from bovine milk was found to be insignificant. The salt penetration into the cheeses was rapid during the first two weeks of ripening, and it continued to diffuse into the samples throughout storage. Proteolysis developed faster in the cheese made from ovine milk than in cheese of bovine milk. The former sample had higher water soluble nitrogen, nonprotein nitrogen, phosphotungustic acid soluble nitrogen, Proteose‐peptone nitrogen and tyrosine levels throughout storage, and the ripening index was higher as well.